For the second time this week, inmates at a western Brazilian prison staged a bloody riot, leaving 33 dead — among them, 30 beheaded and multiple bodies with hearts torn out.

The incident occurred between Thursday night and Friday morning at the Monte Cristo prison in Roraima state, on the border with Venezuela. According to the Brazilian newspaper O Globo, the assailants threw multiple bodies over the gates of the prison after cutting their heads off. Some bodies were also missing their hearts. An image in the local newspaper Roraima em Tempo shows some bodies missing limbs.

In addition to those killed, a total of 74 people, both inmates and guards, were reportedly held hostage throughout the siege until police were able to subdue the attackers.

Early reports, citing regional Justice Minister Uziel Castro, suggest that the riot was an attack on members of the Família do Norte (FDN) drug trafficking gang, tied to the second-largest gang in the country, the Red Command (CV). Castro reportedly told journalists that there was “no riot” in the prison, but rather a calculated massacre, seemingly exclusively of FDN members.

The FDN has been at war with the country’s largest gang, the Primeiro Comando da Capital (PCC), for some months, a war that had recently affected the Monte Cristo prison. The PCC is based in Sao Paulo, Brazil’s largest city, while the CV operates in Rio de Janeiro. Police have found evidence over the past year that indicates the PCC is looking to play a bigger role in Rio de Janeiro, challenging local control.

A confrontation between the two gangs left 11 inmates dead in October, many also beheaded and some burned to death. Authorities reportedly chose to separate members of the two gangs following the incident to prevent repeats, leaving many unanswered questions as to how guards failed to prevent the incident on Friday morning.

Roraima em Tempopublished an image of a note the newspaper claims was found in the prison reading “blood is paid in blood,” allegedly an instruction from the PCC to its members. The prisoners also reportedly possessed gunpowder, cell phones, drugs, other instructional notes from drug gang heads, and pieces of iron that could be used as weapons.

The blood to be paid was spilled on the morning of New Year’s Day in neighboring Amazonas state, at the Anisio Jobim Prison Complex of Manaus (Compaj). Police do call the incident there a riot: a 17-hour episode of violence that left 56 dead and 184 fugitives. While Brazilian Justice Minister Alexandre de Moraes refused to ascribe blame to the FDN gang, claiming that half of those killed did not have a gang affiliation. Inmates who took video of the bodies following the massacre identified the heads of those killed as PCC members, however, though their claims have yet to be officially confirmed.

De Moraes told reporters following the second massacre that Brazil’s prisons “have not gotten out of control.” “It is another difficult situation, Roraima had already had problems previously,” de Moraes argued. “Local authorities were already monitoring this. It is not out of control.”

De Moraes also once again denied that gangs could have been involved in the incident: “This is apparently not retaliation by the PCC towards the Familia do Norte… the gangs had been separated in this prison, so everyone was from the same gang, the PCC.”